Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 201712
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1112 AM MDT Thu Apr 20 2017

.SHORT TERM...(Today through Saturday night)
Issued at 323 AM MDT Thu Apr 20 2017

Main forecast issues will be upcoming precipitation event and how
cold to make low temperatures Friday and Saturday nights. Satellite
showing an amplified flow that now extends from the Pacific into
North America. The flow has become more amplified in the last 24
hours, especially from the eastern Pacific into North America.

At mid levels...models were having their difficulties. They were
tending to be not amplified enough and were a little too far east.
Overall would say the Ukmet and Ecmwf were a little better than the
rest. It looked like the Nam and Gfs were starting better on the low
level thermal field.

Today/tonight...Initial question will be if any thunderstorms and
showers will be ongoing. Right rear quadrant of the jet, which was
the main cause for the thunderstorms continuing through the night,
is still over the forecast area through the late morning/early
afternoon hours. Of note on the precipitation from yesterday
afternoon into tonight, amazing what happens when you have strong
jet lift and negative theta-e lapse rates on a perceived too dry air
mass. Surface dewpoints were from the mid 30s to the lower 40s.

Will be watching the trends as long as possible before making a
final decision. Once the precipitation ends, it looks like we will
have plenty of sun. There also looks to be plenty of cooler air
behind the front driven by north central storm system.

Next storm system starts moving into the area during the night.
There appears to be a slight slowing of the system. Pops continue to
increase through the night. Made adjustments based on this and the
blending with my neighbors. It still appears that some thunderstorms
may still be possible/embedded in the rain in the south and west
later in the night.

Friday/Friday night...Based on the initial analysis, strong ridging
behind the system, and strong jet on the west side of the system,
believe models are too fast with the system and not far enough south
and west with the system at the beginning of the day. And that fits
with the assessment of model slowing mentioned in the previous
period. Also models have changed a little in their path and
evolution of this system from yesterday.

The models have slowed the closing off of the system. Not sure about
this and the subtle shift northward of the system. No matter what,
pops will still be high for the day but there is a little more
uncertainty in regards to this and the amount of qpf than there was
yesterday. Pretty much everything points to having little diurnal
range on Friday, especially in the southwest half. So adjusted
temperatures down a little in this area

Trend of decreasing pops through the night still looks good with the
precipitation pretty much ended by the end of the night. There still
looks to be a decent amount of cloud cover around, especially along
and west of the Colorado border. Am a little concerned that the
models may have too much cloud cover and may have lows too warm,
especially in the eastern portion. Did adjust lows down a little,
mainly in the east.

Saturday/Saturday night...Mid level ridging and drying occurs
through the day as the system pulls away. Dry forecast looks good
with warmer temperatures. At this time the blend looks good with
this and made little to no changes.

For the night, there looks to be little to no cloud cover around.
The question to answer on how cold it get will be how fast the winds
increase, mainly in the west. Right now am expecting lighter winds
than what the output is telling me with the eastern portion of the
area having light winds most of the night. Again I cooled low
temperatures a little. However, I may not be cold enough. As the
forecast stands now, low temperatures are expected to be 33 to 36
which means a lot of frost. Will be adding frost wording to the
forecast. Any colder and freezing conditions instead of frost will
be a problem.

.LONG TERM...(Sunday through Wednesday)
Issued at 323 AM MDT Thu Apr 20 2017

The active weather pattern will continue during this period.  There
will be two opportunities for rainfall with another round possible
outside the forecast period.

The upper level short wave ridge will shift east of the forecast
area Monday ahead of a short wave trough.  A cold front will
accompany this trough, moving through late Monday afternoon.  Due to
the deep dry layer below 600mb, am doubtful any rainfall will occur
with this short wave trough and frontal passage.

After this trough cooler, more seasonal temperatures will return as
zonal upper level flow moves over the Central Plains.  Looking at
specific humidity in the 700-500mb layer, water vapor increases
behind the short wave trough on Monday, which will help facilitate
rainfall production with the later short wave troughs.

The two chances for rainfall will occur Tuesday evening and
Wednesday afternoon/night as a couple upper level short wave troughs
move through the zonal flow.  The GFS and ECMWF are both in fairly
good agreement with the track/speed of these features, with both of
them speeding up the arrival of the short wave troughs over the last
few model runs.

Am not expecting any severe storms on Tuesday or Wednesday due to
the cool temperatures and unfavorable temperature lapse rates. Lapse
rates may be steep enough to generate a thunderstorm, but not much
more than that.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1112 AM MDT Thu Apr 20 2017

Conditions...Mainly VFR at both sites thru 12z Friday...then MVFR
conditions set in for rest of forecast period.

Precip/Wx....None expected thru 03z-05z Friday then VCSH develop
thru 12z. From 12z onward...3-6sm in showers and fog in tandem
with ceilings dropping down to ovc012-030.

Winds........For KGLD...N around 10kts thru 21z...then ENE around
10kts thru 03z Friday. By 03z Friday...a shift to ESE around
10kts w/ gusts to 25kts possible from 14z onward.

For KMCK...NW around 10kts thru 22z...then ENE around 10kts. By
02z Friday...ESE around 10kts w/ gusts to 20kts possible from 15z
onward.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&

$$

SHORT TERM...BULLER
LONG TERM...JTL
AVIATION...JN



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